Thermostat.



H. D. MONTGOMERY.

THERMOSTAT.

APPLICATION FILED FEB. 2!, I917.

1,283,260. Patente 00c, 29, 1918,

WITNESS INVENTUR 2 .HrbertBMoni'fiomem u, .i

UNITED ST PATENT GFFIC'E.

HERBERT D. MONTGOMERY, 0F BROOKLYN, NEW YORK.

THERMOSTAT.

Specification of Letters Patent.

Patented Oct. 29, 1918.

Application filed February 21, 1917. Serial N 0. 150,008.

ments in Thermostats, of which the f0ll0W- is a specification.

y invention relates in general to a thermostat for use in automatic firealarm systems and particularly relates to a cable in- 'cluding twoconductors normally insulated from each other at least one of which isformed of metal having a low fusion point,

designed, when heated to the desired degree of temperature, to completethe electric circuit through the other conductor and thus actuate a firealarm or other heat controlled mechanism.

In one form of device of this character, an inner fusible wire core iscovered with a paper insulation, wrapped spirally about the other,non-fusible conductor and this in turn covered with an outer layer ofinsulating material.

This form of cable, when new or when used under normal condition,generally ives satisfactory service, but after it has een in use forawhile especially when exposed to dampness and other climaticconditions, the insulation appears to deteriorate. As a result knocks orjars on the cable and sometime due to no apparent cause whatsoever, themechanism controlled thereby accidentally functions.

It has been suggested to substitute different insulators from thoseusually used but the trade insists upon a fabric insulation in thesedevices. Further other materials are objectionable amon other reasonsbecause they are prohibitwely expensive and not adapted for thermostaticwork for the insulation must be such that the fusible metal in expandingcan readily break through to make contact with the other conductor.Another possible solution of the problem is to increase the amount ofinsulation used between the conductors but this gives rise to otherdifliculties; it increases the diameter of the cable over what the tradeis accustomed to use; it minimizes the possibility of the fusible metalbreaking through; it is diflicult to bend about angled members, andespecially in locations where heat and moisture are prevalent, it merelyprolongs the life of the cable to a more or less extent, depending uponthe action of the disintegrating agents present.

The primary object of this invention is to provide a simple andinexpensive form of thermostat cable which will preserve its inr tegrityeven under disadvantageous condii tions of service and at the same timewhich will be promptly and sensitively responsive to those heatconditions under which it is designed to react.

Broadly, I attain this object by increasing the normal amount ofinsulating mate rial usually disposed between the conductors andjacketing the cable with covering applied in such a manner that thefibrous material forming the insulation is compressed to bring the twoconductors almost, but not entirely into physical contact.

Other desideratums are to provide a cable of the class described, whichwill be of relatively small diameter, which can be readily bent intosharp angles without breaking down the insulation between the conductorsand which will be reinforced against both external knocks and againstthose influences which have heretofore acted to disintegrate the fabricinsulations used in devices of this character.

As lead has a low melting point and is quite pliable and compressible, Ihave found this metal an excellent material from which to construct theouter jacket.

Various other objects and advantages of the invention will be in partobvious from an inspection of the accompanying drawings and in part willbe more fully set forth in the following particular description of oneform of mechanism embodying my invention, and the invention alsoconsists in certain new and novel features of construction andcombination of parts hereinafter set forth and claimed.

Referring to the accompanying drawings:

Figure 1 is a portion of the side wall of a vessel showing a preferredembodiment of my invention installed therein; and

Fig. 2 is a perspective view of a portion of the thermostat cable with asmall section of its several layers removed to show the construction. 1

The cable part cularly forming the subject-matter of this invention isshown installed as part of an automatic fire alarm system on a vessel,which showing discloses the peculiar adaptability of the invention foruse in a location which may be damp and where the cable is apt to besubjected to jars and knocks. The system includes the cable 3 mounted insupporting brackets l, and leading to some conventional heat actuateddevice indicated diagrammatically by batteries 5 and a call bell 6arranged so that closing the circuit through the pair of conductorshereinalter described in the cable will cause the hell or other deviceto function.

The cable is made up so as to be sold as a complete article ofmanufacture and cut to any desired length. lteterring to the disclosureoi Fig. 2, it will be noted that the cable includes an inner conductor 7or copper inclosed within a tube 8 of metal of relatively low fusingpoint in turn incloseu within an insulation 9 formed of a cotton braid,This insulation among other characteristics is peculiar in that it is ofgreater mass than the insulation usually found in such devices but isheld under such compression that its thickness is even less than thethicknessol the known forms. This compressed insulation has a tendencyto enpand. when relieved or the compressing force so as to follow up anincasing jacket herematter described should heat conditions presentcause this jacket to enlarge its internal diameter. The insulation iswound spirally with a second conductor 10 preierably of relatively highfusion point, such as copper wire. This second conductor is in turncovered by a second tube of insulation 11 of any suitable material.

The cable is thus constructed and then a thin lead jacket 12 is drawn onto the construction in such a way as to compress the insulation 9 and tohold the same coinpress ed. This compression of the oonstruction willcause the outer conductor 10 to become embedded in the insulation 9 soas to ring the conductors 7 and 10 into relatively close relationshiwith a thin layer of the compressed fabric insulation and the fusiblemetal positioned therebetween. The amount of insulating material is soproportioned and the degree of pressure so regulated that the innerconductor when fused can readily break throughthe compressed layerbetween the conductors and at the same time provide the maximum possibleamount of insulation.

Compressing the insulation appears to enhance its" insulatingproperties, insures the complete covering of the inner conductor, eventhough the insulation be of some porous material, and tends to prolongthe life of the same. 7

Incidentally, theouter lead jacket, while of heat therethrough, toaffect the fusion of the inner conductor, provides a waterproof coveringfor the device, Also it acts to confine the fused metal and thus tendsto insure t5 the electric circuit closing contact between oiferinglittle if any obstacle to the passage season the outer conductor and thefused inner conductor. The lead jacket can be easily worked and thecomplete cable is flexible thus permitting its use around corners andinto angles as shown at the rafter in Fig. 1. The lead jacket acts toabsorb knocks on the device which knocks merely tend to dent the outerjacket or shell rather than to transmit the knock therethrough toaccidentally short circuit the conductors.

The peculiar construction of the inner conductor also is novel in thatthe high electric conducting properties of a copper core may be utilizedand at the same time the low fusing metal is provided so as to fuseunder low temperature conditions. Making the core oi the conductor ofrelatively low priced copper attains som saving in cost of the r'usiblemetal.

Under some situations, as where the cable is to be positionedin coalbunkers, it may be desired to form the lead jacket 12 or a portion ofthe same of a thickness greater than the usual jacket. in addition to oreven supplementing the lead jacket, a flexible steel jacket may be usedto give the necessary resistance and protection.

Having thus described my invention, I claim:

l. in a-thermostat, a flexible thermostatic cable including an innerconductor having a relatively low point of fusion, a fabric insulationsurrounding said inner conductor, said insulation being held compressedand capable oi expanding when released, a second conductor wrappedspirally about said compressed fabric insulation, and positionedrelatively close to the inner'conductor, a covering of insulatingmaterial for said sec-' ond conductor, and a lead jacket drawn on 10:said cable and acting to hold the insulation compressed, said innerconductor adapted to break. through the compressed insulation whenheated to its point of fusion and to come into permanent electricallycircuit clos- 111 ing engagement with the second conductor.

2. In a thermostat, a flexible thermostatic cable including an innerconductor havin a relatively low point of fusion, a compressi 1einsulation surrounding said conductor, a sec- 1 end conductor positionedexteriorly of the insulation, a secondinsulation covering the secondconductor and a lead jacket drawn on the cable and acting to hold thesecond conductor embedded in the first named in- 1 sulation and to holdthis first named insulation under compression to bring the con ductorsrelatively close to each other, said inne'r'conductor adapted to breakthrough the portion of the compressed insulation (118- 12 posed betweenthe conductors when the inner conductor is heated to its point of fusionand thus electrically connect the conductors.

3. A thermostatic cable including a pair of conductors, means normallymaintaining 1 the conductors insulated from each other, expansible meansfor electrically connecting the conductors on an abnormal raise intemperature, compressed insulating material in- I insulating closingsaid conductors and means, and a flexible metallic jacket closelyengaging the material'and acting to hold the same under compression,said jacket constituting a means for conducting heat along the cable andconstituting a means for retaining the expansible means in operativeposition relative to the conductors.

4i. A thermostatic cable including an inner copper conduction a metaltube of relatively low fusing point inclosing said copper conductor, aninsulation surrounding said tube, said insulation being held compressed,a second conductor Wound spirally about the insulation, a second tube ofinsulation inclosing said spirally Wound conductor and a flexiblemetallic jacket drawn over said second tube of insulation to hold thefirst named insulation under compression.

Signed at New York in the county of New not and State ofNeW York day ofFebruary A. l). 1917.

HERBERT n. MONTGUMERY,

this fifteenth 25

